1. Field of the Invention
One aspect of the invention relates to digital image processing using techniques to efficiently process digital images.
2. Description of the Related Art
Video systems convey one component representative of luminance, luma, and two other components representative of color, chroma. In many systems, luma and chroma are represented as Y′CbCr with Y representing luma and Cb and Cr representing chroma.
In order to reduce bandwidth requirements for sending video across lower bitrate data streams images are typically subsampled such that their chroma components are reduced. Because users are less sensitive to the position and motion of color in comparison to luminance, the chroma detail of a video can be subsampled without incurring a perceptible loss of image quality. For example, a full bandwidth signal that is four pixels across and four pixels high (4:4:4 Y′CbCr) image may be subsampled to a 4:2:2 Y′CbCr scheme wherein the chroma components are only sampled at half the data rate of the luma component vertically. The full bandwidth signal can be subsampled to a 4:2:0 Y′CbCr scheme wherein the chroma components are only sampled at half the data rate of the luma component both horizontally and vertically.
While this scheme allows transmission of video images at a lower overall bandwidth, the encoder which eventually displays the subsampled images needs to upsample and scale the subsampled images in order to display a final video in high resolution to a user. In order to upsample and scale subsampled image data, typical display systems include two separate hardware modules for 1) upsampling the chroma samples and 2) changing the resolution of the input source image/frame to match the display resolution.